There are many situations, such as immunoprecipitation, in the context of protein research that result in low-concentration (<1 micromolar) solutions of proteins of interest. For example, mass spectrometric immunoassay (MSIA) is a high throughput form of immunoprecipitation that may involve simultaneous handling of up to 96 samples. Until recently, the major analytical modality for MSIA was MALDT/TOF mass spectrometry, in which eluted proteins are stamped onto a MALDI target and immediately dried prior to analysis. For many proteins, electrospray ionization (ESI) mass spectrometry provides advantages over MALDI-MS. Attempts to couple MSIA with ESI/MS have been limited in throughput capability because samples have to be eluted individually and introduced into the ESI mass spectrometer one at a time to avoid adsorptive and/or oxidative protein losses while samples sit in autosampler vials (for minutes to hours) waiting to be injected. Thus, reagents and methods to limit such protein loss in samples of interest are needed.
Blood plasma/serum samples are susceptible to artifactual oxidative damage over time during storage in the freezer (even at temperatures as low as −80° C.). This may be due to chemistries that occur in the solid phase or chemistries that occur upon sample thawing and temporary storage in the liquid state. Importantly, this storage-associated oxidative damage may adversely or artifactually affect the outcome of clinical or other analytical measurements made on proteins and other molecules in the sample—leading to inaccurate results. Thus reagents and methods to limit such artifactual oxidation in stored plasma/serum samples are of interest.